---
id: CVE-2026-84970
title: >-
  A numeric truncation weakness exists in the JSON parsing component of the
  MongoDB C++ Driver's BSON library
summary: >-
  A numeric truncation weakness exists in the JSON parsing component of the
  MongoDB C++ Driver's BSON library. An actor who controls the text that an
  embedding application hands to the library's public JSON parsing interface,
  when that tex…
severity: medium
cvss: 6.2
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H'
cwe:
  - CWE-681
vendor: mongodb
product: c++_driver
affected:
  - 'c++_driver >= 3.2.0, < 4.5.2'
patched:
  - c++_driver 4.5.2
published: '2026-09-03'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T19:47:31.733'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-84970'
references:
  - url: 'https://jira.mongodb.org/browse/CXX-3547'
    label: cna@mongodb.com
tags:
  - nvd
epss: 0.00124
epssPercentile: 0.01815
ingestedAt: '2026-09-10T20:04:29.977Z'
---

## Overview

A numeric truncation weakness exists in the JSON parsing component of the MongoDB C++ Driver's BSON library. An actor who controls the text that an embedding application hands to the library's public JSON parsing interface, when that text is very large, can cause the library to read memory beyond the supplied buffer and return it to the caller, to silently accept only part of the input as a complete document, or to terminate the process. No MongoDB server, credentials, or non-default configuration is required; the effect is confined to the process that uses the library.

## Affected

- `c++_driver >= 3.2.0, < 4.5.2`

## Remediation

Upgrade past the affected range:

- `c++_driver 4.5.2`